We now have the clearest picture yet of what the inside of wood looks like on the nanoscale. This improved understanding could help efforts to use it as an alternative to steel and concrete in the construction of tall buildings, which would reduce greenhouse gas emissions.
Paul Dupree at the University of Cambridge and his colleagues used low temperature scanning electron microscopy 鈥� a high-resolution imaging tool that scans surfaces using a beam of electrons 鈥� to get a closer look at living wood鈥檚 internal structure. This had previously only been done on dead wood such as logs and chippings, which might have altered the final images because the material was dried out.
The team looked at spruce, ginkgo and poplar trees and froze the samples in order to take precise measurements. Inside the cell walls are long chains of cellulose that bundle together into cylinders called macrofibrils. They found bundles that were over 10 nanometres long 鈥� around three times bigger than cellulose structures measured in previous research 鈥� in both hardwood (poplar) and softwood (ginkgo and spruce).
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The team thinks that these cylinders are what give wood its strength. 鈥淭he presence of these macrofibrils helps us explain how the strength and flexibility of wood might arise,鈥� says Dupree, although exactly how they form is still unknown.
Understanding this can help overcome the current challenges of using wood for buildings, such as twisting when it dries and splintering, because we can better understand its properties. By knowing the arrangement of macrofibrils and their structure, we could engineer wood to have desirable traits, either by breeding trees with a particular wood structure or by treating the wood chemically, says Dupree.
That may be some time off, says Paul Knox at the University of Leeds, UK. 鈥淭his work opens the way for an improved and detailed nanoscale understanding of wood structures and properties, however direct application to industries that utilise wood biomass would be somewhat in the future.鈥�
Frontiers in Plant Science
